1. Field of the Invention
The present invention relates generally to a digital camera, and more particularly, to a method and apparatus which enables the digital camera to be rapidly driven while maintaining low power consumption.
2. Description of the Related Art
Modern mobile terminals are multi-functional. For example, a cellular phone provides voice communication as well as a plurality of additional functions, such as Near Field Communication (NFC), music file reproduction, Digital Multimedia Broadcasting (DMB) service reception, and image photographing. While it has been possible for one mobile terminal to provide various functions, as described above, an active power control is required due to the inherent increased power consumption.
In order to efficiently manage power, a mobile terminal having a camera function shifts to a photographing standby state when a photographing request is not input for a period of time when a photographing mode is set. In the photographing standby state, Auto Exposure (AE) and Auto White Balance (AWB) are not performed, or a fine adjustment of a lens motor for Auto Focus (AF) is forbidden, in order to reduce power consumption. Thereafter, either when a photographing request continues not to be input, or when a user input connected with a camera is not sensed, the photographing mode is automatically terminated or the output of a display screen is stopped. Accordingly, power applied to an image sensor is interrupted, and loading of a camera application program is canceled.
When it is necessary to store an image obtained through photographing, or to perform a specific function in a photographing activation state, the mobile terminal shifts to the standby state, and returns to the photographing activation state after the specific function has been completed. For example, although a cellular phone is in a photographing activation state, where all components connected with an image photographing function are activated, the cellular phone preferentially performs an operation, such as communication or message checking, when receiving a call or text message. In this case, a photographing mode is terminated or shifts to a standby state. When the photographing shifts to the standby state, the cellular phone returns to the photographing activation mode when the communication has been terminated or when the message has been checked. However, when the standby time becomes longer than a given period of time, the photographing mode is completely terminated.
When a photographing mode is set in a mobile terminal, the time required for shifting to an activation state is one second to two seconds, a procedure of which is shown in FIG. 1. Referring to FIG. 1, in order to activate a camera function in response to a photographing mode setup request of the user, the mobile terminal drives an image sensor by applying power to the image sensor, and loads a photographing program into a memory. Then, the mobile terminal initializes the image sensor, and sets the image sensor according various camera setup values, such as initialization of a zoom function, image size, ISO, and exposure time, and shifts to an activation state where it is possible to directly perform an image photographing in response to a photographing key input or the like.
Of the aforementioned power management schemes, the scheme of terminating the photographing mode or interrupting the output of the display unit in the mobile terminal when a period of time has elapsed has a problem in that the user cannot actively use the low power function of the camera.
In addition, only AF, AE, and AWB functions are interrupted in the standby state, which only minimally reduces power consumption.
Also, when the photographing standby period of time is lengthened due to another cause, such as call incoming, and thus the photographing mode is terminated, the user will probably desire to again set the photographing mode and to enter the activation state. However, since the photographing mode has already been terminated, it is possible to momentarily set the activation state, rendering it necessary to reset the photographing mode step by step from the beginning based on a procedure, as shown in FIG. 1. In this case, a waiting time of the user increases, so that the user may miss an opportunity to photograph a desired scene.